Before Getting Started

Determine whether you want to use a deep-cycle flooded, AGM or gel battery.

Step 1: Determine Your Battery Voltage And How Many Batteries To Use

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Based on your system voltage, you must first decide which battery is needed and how many to use in order to meet your requirements. For example, you may connect a series of eight 6V batteries, six 8V batteries or four 12V batteries for a 48-volt system. The size of your battery compartment, your performance requirements and costs may limit your options.

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Make sure there is enough space between batteries to allow for minor battery expansion that occurs during use and to allow proper airflow to keep battery temperature down in hot environments.

TIP

Connecting batteries in series does not increase the capacity of the batteries; it simply increases the overall voltage to meet your system requirements. Once your voltage requirements are met, and if space allows, you can double the batteries in a parallel connection — thereby doubling your battery capacity. See diagrams below.

Series Connect

Parallel Connect

Series/Parallel Connect

To increase voltage, connect batteries in series. This will not increase the system capacity.Example Two T-105, 6V Batteries rated at 225AH Connected in SeriesSystem Voltage 6V + 6V = 12V System Capacity = 225AH

To increase capacity, connect batteries in parallel. This will not increase the system voltage.Example Two T-105, 6V Batteries rated at 225AH Connected in ParallelSystem Voltage 6V System Capacity = 225AH + 225AH = 450AH

To increase both voltage and amp-hour capacity, connect batteries in series/parallel.

Step 2: Choose Your Best Battery Model

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When choosing your battery model, first consider your battery compartment space, as this may limit your options. Within your size restrictions you may have several battery options to choose from. For example, you can use a T-605, T-105 or T-125 in the same space, as they are the exact same physical size. The difference between these batteries is the amount of energy they offer.

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Next consider your energy needs. If replacing an existing battery, use it as a reference point. If your old battery provided enough energy, it can be replaced with a similar capacity battery. If you need more energy you can size up, or if you need less energy you can size down.

TIP If you do not know what battery to use, contact your equipment manufacturer for their recommended battery specification. Trojan Battery also offers outstanding technical support provided by full-time applications engineers to help you select your ideal batteries.

Step 3: Select Your Best Terminal

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Finally determine which terminal option best meets your needs based on the type of cable connections you plan to use. Look for the terminal(s) available for the battery you have selected.

TIP Make sure you use the proper cable size when connecting your batteries so the connections do not overheat. For information regarding correct wire sizes you can refer to the National Electric Code, Trojan Battery User’s Guide, or contact Trojan’s live technical support at 800.423.6569.

Battery Type

Lead acid batteries are generally classified by application (what they are used for) and by construction (how they are made). Deep-cycle batteries are used for various types of applications specific such as RV, golf cars, renewable energy, and marine.

There are two popular construction types: flooded batteries (wet) and VRLA batteries (Valve Regulated Lead Acid). In the flooded types, the electrolyte is a solution of sulfuric acid and water that can spill out if the battery is tipped over. In VRLA batteries, the electrolyte is suspended in a gel or a fiberglass-mat (AGM technology), allowing these batteries to be mounted in a variety of positions.

Before getting started, be sure to identify the type of battery involved. This section addresses the charging and maintenance for both deep-cycle flooded and VRLA batteries.

Batteries should be carefully inspected on a regular basis in order to detect and correct potential problems before they can do harm. It is a great idea to start this routine when you first receive the batteries are first received.

Inspection Guidelines

1. Examine the outside appearance of the battery.

Look for cracks in the container.

The top of the battery, posts, and connections should be clean, free of dirt, fluids, and corrosion. If batteries are dirty, refer to the Cleaning section for the proper cleaning procedure.

Repair or replace any damaged batteries.

2. Any fluids on or around the battery may be an indication that electrolyte is spilling, leaching, or leaking out.

Leaking batteries must be repaired or replaced.

3. Check all battery cables and their connections.

Look closely for loose or damaged parts.

Battery cables should be intact; broken or frayed cables can be extremely hazardous.

Replace any cable that looks suspicious.

4. Tighten all wiring connections to the proper specification (see below). Make certain there is good contact with the terminals.

Proper Torque Values for Connection Hardware

Flooded

VRLA

Automotive

50 – 70 in-lbs

Button

90 – 100 in-lbs

Side

70 – 90 in-lbs

LT

100 – 120 in-lbs

Wingnut

95 – 105 in-lbs

LPT

95 – 105 in-lbs

Stud

120 – 180 in-lbs

LT

100 – 120 in-lbs

WARNING: Do not overtighten terminals. Doing so can result in post breakage, post meltdown, or fire.

Testing

Visual inspection alone is not sufficient to determine the overall health of the battery.

Both open-circuit voltage and specific gravity readings can give a good indication of the battery’s charge level, age, and health. Routine voltage and gravity checks will not only show the state of charge but also help spot signs of improper care, such as undercharging and over-watering, and possibly even locate a bad or weak battery. The following steps outline how to properly perform routine voltage and specific gravity testing on batteries.

I. Specific Gravity Test (Flooded batteries only)

Do not add water at this time.

Fill and drain the hydrometer 2 to 4 times before pulling out a sample.

There should be enough sample electrolyte in the hydrometer to completely support the float.

Take a reading, record it, and return the electrolyte back to the cell.

To check another cell, repeat the 3 steps above.

Check all cells in the battery.

Replace the vent caps and wipe off any electrolyte that might have been spilled.

Watering

FLOODED BATTERIES ONLY

Flooded batteries need water.

More importantly, watering must be done at the right time and in the right amount or the battery’s performance and longevity suffers.

Water should always be added after fully charging the battery. Prior to charging, there should be enough water to cover the plates. If the battery has been discharged (partially or fully), the water level should also be above the plates. Keeping the water at the correct level after a full charge will prevent having to worry about the water level at a different state of charge.

Depending on the local climate, charging methods, application, etc., Trojan recommends that batteries be checked once a month until you get a feel for how often your batteries are need watering.

Important Things to Remember

Do not let the plates get exposed to air. This will damage (corrode) the plates.

Do not fill the water level in the filling well to the cap. This most likely will cause the battery to overflow acid, consequently losing capacity and causing a corrosive mess.

Do not use water with a high mineral content. Use distilled or deionized water only.

CAUTION: The electrolyte is a solution of acid and water so skin contact should be avoided.

Step-By-Step Watering Procedure

Open the vent caps and look inside the fill wells.

Check electrolyte level; the minimum level is at the top of the plates.

If necessary add just enough water to cover the plates at this time.

Put batteries on a complete charge before adding any additional water (refer to the Charging section).

Once charging is completed, open the vent caps and look inside the fill wells.

Add water until the electrolyte level is 1/8″ below the bottom of the fill well.

A piece of rubber can be used safely as a dipstick to help determine this level.

Storage

Periods of inactivity can be extremely harmful to lead acid batteries. When placing a battery into storage, follow the recommendations below to ensure that the battery remains healthy and ready for use.

Freezing. Avoid locations where freezing temperature are expected. Keeping a battery at a high state of charge will also prevent freezing. Freezing results in irreparable damage to a battery’s plates and container.

Charger Selection

Most deep-cycle applications have some sort of charging system already installed for battery charging (e.g. solar panels, inverter, golf car charger, alternator, etc.). However, there are still systems with deep-cycle batteries where an individual charger must be selected. The following will help in making a proper selection.

There are many types of chargers available today. They are usually rated by their start rate, the rate in amperes that the charger will supply at the beginning of the charge cycle. When selecting a charger, the charge rate should be between 10% and 13% of the battery’s 20-hour AH capacity. For example, a battery with a 20-hour capacity rating of 225 AH will use a charger rated between approximately 23 and 30 amps (for multiple battery charging use the AH rating of the entire bank). Chargers with lower ratings can be used but the charging time will be increased.

Trojan recommends using a 3-stage charger. Also called “automatic”, “smart” or “IEI” chargers, which prolong battery life with their programmed charging profile. These chargers usually have three distinct charging stages: bulk, acceptance, and float.

Charging

Charging batteries properly requires administering the right amount of current at the right voltage. Most charging equipment automatically regulates these values. Some chargers allow the user to set these values. Both automatic and manual equipment can present difficulties in charging. Tables 2 & 3 list most of the necessary voltage settings one might need to program a charger. In either case the original instructions for your charging equipment should also be referenced for proper charging. Here is list of helpful items to remember when charging.

Become familiar with and follow the instructions issued by the charger manufacturer.

Batteries should be charged after each period of use.

Lead acid batteries do not develop a memory and do need not be fully discharged before recharging.

Charge only in well-ventilated areas. Keep sparks or flames away from a charging battery.

Equalizing

FLOODED BATTERIES ONLY

Equalizing is an overcharge performed on flooded lead acid batteries after they have been fully charged.

It reverses the buildup of negative chemical effects like stratification, a condition where acid concentration is greater at the bottom of the battery than at the top. Equalizing also helps to remove sulfate crystals that might have built up on the plates. If left unchecked, this condition, called sulfation, will reduce the overall capacity of the battery.

Many experts recommend that batteries be equalized periodically, ranging anywhere from once a month to once or twice per year. However, Trojan only recommends equalizing when low or wide ranging specific gravity (>0.030) are detected after fully charging a battery.

Step-By-Step Equalizing

Verify the battery(s) are flooded type.

Remove all loads from the batteries.

Connect battery charger.

Set charger for the equalizing voltage (See Table 2 in the Charging section). If your charger doesn’t have an equalization mode, you can unplug the charger and re-plug it back in. This also will conduct the equalization charge.

Start charging batteries.

Batteries will begin gassing and bubbling vigorously.

Take specific gravity readings every hour.

Equalization is complete when specific gravity values no longer rise during the gassing stage.

Watering Diagram

But more importantly, watering must be done at the right time and in the right amount or the battery’s performance and longevity suffers.

General Watering Instructions:

Add water, never acid, to cells (distilled water recommended)

DO NOT OVERWATER

For fully charged standard deep-cycle batteries, add water to the level of 1/8 below bottom of vent well (see diagram A below)

For fully charged Plus Series batteries, add water to the maximum water level indicator (see diagram B below)

If the batteries are discharged, only add water if the plates are exposed. Add just enough water to cover the plates, then charge the batteries. Once fully charged, add water to the proper level indicated above

Tips For Maximizing Your Battery Life

Charge your batteries fully after each period of use. Allowing your batteries to sit in a low state of charge for extended periods will decrease their capacity and life.

If you store your batteries for an extended period of time, be sure to charge them fully every 3 to 6 months. Lead acid batteries will self-discharge 5% to 15% per month, depending on the temperature of the storage conditions.

Monitor battery voltage and specific gravity of the electrolyte regularly to verify full recharging. As a general rule of thumb, the total amps from your PV panels should be sized between 10% and 20% of the total amp-hours (Ah) of the battery pack.

Many charge controllers have equalization settings that you can set to help ensure the health of your batteries. Equalize your batteries at least once per month for 2 to 4 hours, longer if your batteries have been consistently undercharged.

System Voltage

Voltage Settings

6V

12V

24V

36V

48V

Daily Charge

7.4

14.8

29.6

44.5

59.3

Float Charge

6.7

13.5

27

40.5

54

Equalize Charge

8.1

16.2

32.4

48.6

64.8

Water your batteries regularly. Flooded, or wet cell batteries require watering periodically. Check your batteries once a month after installation to determine the proper watering schedule. Add water after fully charging the battery and use distilled water.

For procedures on watering, checking battery voltage and other maintenance instructions, refer to our battery maintenance section for more details.